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Direct methods and simulated annealing: a hybrid approach for powder diffraction data
Author(s) -
Altomare Angela,
Caliandro Rocco,
Cuocci Corrado,
Giacovazzo Carmelo,
Moliterni Anna Grazia Giuseppina,
Rizzi Rosanna,
Platteau Cyril
Publication year - 2008
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889807054192
Subject(s) - simulated annealing , powder diffraction , direct methods , diffraction , minification , annealing (glass) , monte carlo method , materials science , crystal structure , algorithm , computer science , statistical physics , crystallography , chemistry , physics , mathematical optimization , mathematics , optics , statistics , composite material
The solution of crystal structures from powder data using direct methods can be very difficult if the quality of the diffraction pattern is low and if no heavy atoms are present in the molecule. On the contrary, the use of direct‐space methods does not require good quality diffraction data, but if a molecular model is available, the structure solution is limited principally by the number of degrees of freedom used to describe the model. The combination of the information contained in the electron density map (direct methods) with the Monte Carlo method, which uses simulated annealing as a global minimization algorithm (direct‐space techniques), can be a useful tool for crystal structure solution, especially for organic structures. A modified and improved version of this approach [Altomare et al. (2003), J. Appl. Cryst. 36 , 230–238] has been implemented in the EXPO2004 program and is described here.